1. Field of the Invention
The present invention relates to a ladder working limit based ladder stopping device for vehicle equipped with a vertically and horizontally swingable and extensible ladder (or a fire engine truck).
2. Description of the Prior Art
In an aerial ladder truck of the type described, the vertical swing and extension of the ladder are carried out by oil pressure. Thus, a ladder vertical angle indicator and a ladder extension indicator are separately attached to the truck. The operator of the ladder carries out the operation of the ladder while watching said two indicators in such a manner that when he finds that the ladder approaches a dangerous condition, he stops the operation and then handles the ladder so as to avoid the danger. In order to determine whether the ladder is in a dangerous condition or not, he reads the indicated values on said two indicators and checks them with a conversion table or the like to find the bending moment acting around the pivoted point on the ladder. With such procedure, however, there is a disadvantage that it is impossible to take a quick and proper measure. Another disadvantage is that whether the ladder has got out of the danger or not cannot be immediately ascertained.